1. Field of the Invention
The present invention relates to extrusion molding of a weather strip onto the peripheral edge of a windshield glass, and specifically to extrusion molding of such a weather strip having a partly modified cross section.
2. Description of the Prior Art
As shown in FIG. 1, a weather strip 4 is provided around a windshield glass 3 of an automobile. Noting FIGS. 20(A) through 20(D), the weather strip 4 should include an upper portion 4A and a pair of side portions 4C, the portions 4A and 4C having different cross sections from each other. Specifically, as shown in FIG. 20(C), the side portion 4C is required to have a groove 8 extending along a side edge of the windshield glass 3, while the upper portion 4A is not required to have such a groove 8, as shown in FIG. 20(B).
A technique of extruding such a weather strip 4 having a partly modified cross section is disclosed in Japanese Laid-Open Patent Publication No. 3-128721. According to this technique, as shown in FIGS. 22(A1) through 22(D2), extrusion molding is carried out by using a fixed die having an orifice 210 and a movable die having an orifice 220, the movable die being movable in relation to the fixed die. Thus, the orifices 210 and 220 overlap each other to form a portion (i.e. geometrical Boolean product) which defines a practical orifice, and a weather strip having a cross section conforming to the practical orifice in shape is extruded. For example, the orifice 210 and 220 are disposed in such a positional relationship as shown in FIG. 22(B1) to extrude a weather strip portion corresponding to the upper portion 4A which has no groove 8 adjacent to the windshield glass 3. On the contrary, the orifice 210 and 220 are disposed in such a positional relationship as shown in FIG. 22(C1) to extrude a weather strip portion corresponding to the side portion 4C which has the groove 8 adjacent to the windshield glass 3. This results in extrusion molding of the weather strip as shown in FIG. 20(D).
Though this technique is quite effective to integrally extrude such a weather strip 4 having a partly modified cross section, the weather strip 4 is molded separately from the windshield glass 3, so that the weather strip 4 thus molded must be fitted on the peripheral edge of the windshield glass 3. Disadvantageously, there will occur a problem that the weather strip 4 is apt to be twisted during the fitting process. Furthermore, the weather strip 4 may move along the peripheral edge of the windshield glass 3, that is, the upper portion 4A or the side portion 4C of the weather strip 4 may be positioned on the corner edge of the windshield glass 3, though these portions 4A, 4C should be precisely positioned on the upper edge and the side edge of the windshield glass 3, respectively.
U.S. Pat. No. 5,057,265 teaches a technique to form a windshield glass/weather strip assembly. According to the technique, as shown in FIG. 21, extrusion molding is carried out by moving a die 331 having an orifice 331a along the peripheral edge of the windshield glass 3. This assures the weather strip 4 to be extruded along the peripheral edge of the windshield glass 3, thereby to form a windshield glass/weather strip assembly. Thus, the technique can provide the weather strip directly molded on the peripheral edge of the windshield glass 3, eliminating the process of fitting the weather strip on the peripheral edge of the windshield glass 3. It should be noted that the weather strip molded in accordance with the above U.S. Pat. No. 5,057,265 has a uniform cross section. Also, weather strip 4 is formed of urethane having less weatherproof property and is mounted on only the inboard side. Further, the die 331 is moved along the peripheral edge of the windshield glass 3 while contacting thereto. Therefore, if there is a variation in the size of the windshield glass 3, the variation is directly reflected in the external size of the windshield glass/weather strip assembly.
Combination of the technique shown in FIGS. 22(A1) through 22(D1), i.e. molding by moving the movable die in relation to the fixed die so as to change the shape of the practical orifice and the technique shown in FIG. 21, i.e. extrusion molding by the die traveling along the peripheral edge of the windshield glass might be expected to provide a weather strip having a partly modified cross section and molded on the peripheral edge of the windshield glass. However, the combination of the technique shown in FIGS. 21 and 22(A1) through 22(D1) can form only the weather strip having limited cross section.
As shown in FIGS. 22(B2) and 22(C2), the weather strip 4 has on the outboard side thereof a projection 6a extending toward the center of the windshield glass 3, the projection 6a being disposed in contact with the windshield glass 3 at some parts of the weather strip 4 and apart therefrom at other parts. As shown in FIG. 22(A1), the fixed die should be formed with an orifice 210 having the same width as the projection 6a and extending vertically as seen in the drawing. The movable die having an orifice 220 is vertically movable in the orifice 210 so as to change the level where the projection 6a is formed. If the weather strip 4 is molded separately from the windshield glass 3, there would be no problem of interference between the movable die and the windshield glass 3, permitting execution of the extrusion process as shown in FIGS. 22(A1) through 22(D2). If it is, however, desired to carry out extrusion molding along the peripheral edge of the windshield glass 3, there occurs an interference between the windshield glass 3 and the movable die, which would inhibit execution of the process in FIGS. 22(A1) through 22(D2). If the movable die is so designed as to avoid such interference with the windshield glass 3, it is possible to mold a weather strip having a cross section which is partly different in thickness H (FIG. 22(D2)) but not possible to form a groove 8. In order to form the groove 8, it is required to provide the movable die with a wall for defining the groove 8 and this wall would inevitably interfere with the windshield glass.